﻿
//elf文件中使用的hash函数如下：
unsigned long elf_hash(const char *name)
{
	unsigned long h=0,g;
	while(*name){
		h=(h<<4)+(*name++);
		if(g=h&0xf0000000)
			h^=g>>24;
		h&=-g;
	}
	return h;
}

// RS Hash Function
unsigned int RSHash(char* str)
{
    unsigned int b = 378551;
    unsigned int a = 63689;
    unsigned int hash = 0;

    while (*str)
    {
        hash = hash * a + (*str++);
        a *= b;
    }

    return (hash & 0x7FFFFFFF);
} 
 
// JS Hash Function
unsigned int JSHash(char* str)
{
    unsigned int hash = 1315423911;

    while (*str)
    {
        hash ^= ((hash << 5) + (*str++) + (hash >> 2));
    }

    return (hash & 0x7FFFFFFF);
}
 
// P.J.Weinberger Hash Function
unsigned int PJWHash(char* str)
{
    unsigned int BitsInUnignedInt = (unsigned int)(sizeof(unsigned int) * 8);
    unsigned int ThreeQuarters    = (unsigned int)((BitsInUnignedInt * 3) / 4);
    unsigned int OneEighth        = (unsigned int)(BitsInUnignedInt / 8);

    unsigned int HighBits         = (unsigned int)(0xFFFFFFFF) << (BitsInUnignedInt - OneEighth);
    unsigned int hash             = 0;
    unsigned int test             = 0;

    while (*str)
    {
        hash = (hash << OneEighth) + (*str++);
        if ((test = hash & HighBits) != 0)
        {
            hash = ((hash ^ (test >> ThreeQuarters)) & (~HighBits));
        }
    }

    return (hash & 0x7FFFFFFF);
} 
 
// ELF Hash Function
unsigned int ELFHash(char* str)
{
    unsigned int hash = 0;
    unsigned int x    = 0;

    while (*str)
    {
        hash = (hash << 4) + (*str++);
        if ((x = hash & 0xF0000000L) != 0)
        {
            hash ^= (x >> 24);
            hash &= ~x;
        }
    }

    return (hash & 0x7FFFFFFF);
}

// BKDR Hash Function
unsigned int BKDRHash(char* str)
{
    unsigned int seed = 131;  //  31 131 1313 13131 131313 etc..
    unsigned int hash = 0;

    while (*str)
    {
        hash = hash * seed + (*str++);
    }

    return (hash & 0x7FFFFFFF);
}

// SDBM Hash Function
unsigned int SDBMHash(char* str)
{
    unsigned int hash = 0;

    while (*str)
    {
        hash = (*str++) + (hash << 6) + (hash << 16) - hash;
    }

    return (hash & 0x7FFFFFFF);
}

// DJB Hash Function
unsigned int DJBHash(char* str)
{
    unsigned int hash = 5381;

    while (*str)
    {
        hash += (hash << 5) + (*str++);
    }

    return (hash & 0x7FFFFFFF);
}

// AP Hash Function
unsigned int APHash(char* str)
{
    unsigned int hash = 0;
    int i;

    for (i = 0; *str; i++)
    {
        if ((i & 1) == 0)
        {
            hash ^= ((hash << 7) ^ (*str++) ^ (hash >> 3));
        }
        else
        {
            hash ^= (~((hash << 11) ^ (*str++) ^ (hash >> 5)));
        }
    }

    return (hash & 0x7FFFFFFF);
}